Advanced integrated circuit fabrication processes, such as CMOS can produce chips with low power consumption, high logic density and high speed of operation. However, these modern processes manufacture integrated circuits that operate at low voltages, due to the lowered breakdown voltages of the transistors that are fabricated. These low voltage IC's are difficult to interface with circuits operating at higher voltage levels, unless special processes are used that can produce low voltage and high voltage devices in the same IC, but these special processes can have disadvantages such as limited performance capabilities.
One particular area of technology using low voltage ICs, but required to interface to higher voltage circuits is implantable medical devices for the purpose of functional electrical stimulation (FES). Such devises stimulate nerve bundles with electrodes in close proximity to the nerve tissue.
A differential pair is a very important circuit in the design of many analog circuits, such as for example, operational amplifiers (op amps) or differential amplifiers. Differential pairs are used as the front end input stage of op amps. The ability to process high voltage signals using high voltage tolerant circuits such as differential pairs and op amps, with integrated circuits built using low voltage advanced CMOS processes, is highly desirable.